Taipei, Aug. 7 (CNA) Economics Minister Chang Chia-juch announced his resignation Thursday over the "humiliation" lodged at his ministry for its alleged role in the deadly Kaohsiung blasts, even as the president and premier are committed to keeping him on the job. The Economics Ministry has been blamed for allegedly failing to keep close tabs on the petrochemical industry before the July 31 blast, which killed 30 people and injured more than 300. In his resignation announcement, Chang bemoaned perceived political motivations behind the blame game. "Some political figures have continuously used misinformation in political manipulation, taking every possible approach to pressure, smear and humiliate our colleagues" in the ministry, he said. Referring to himself in the third person, he said "(I) have seen some political figures who put only elections and political positions in their minds without real concern for the victims and reconstruction (efforts). This is extremely saddening." He is also "physically and mentally exhausted" after witnessing major policies fail to gain momentum over the past year and a half "due to a hostile political environment." He criticized the opposition for "blocking the bills (in the Legislature), failing to differentiate right from wrong, disregarding public interest, and continuously paralyzing the implementation of all government affairs." Altogether, the political fighting has left him "extremely worried about the future of the nation," he said, noting that since the explosions, the nation has come to a standstill amid finger pointing. But he said he "will shoulder all the blame" in a bid to get "ruling and opposition parties to set aside political interests and work together to resolve the difficulties of the present." Meanwhile, Kaohsiung Deputy Mayor Wu Hong-mo, who tendered his resignation shortly before Chang, confirmed that an underground waterway that likely indirectly caused the blasts was built by the city government while he was a section chief at the Water Resources Bureau. The "phantom culvert" has been at the center of the probe for days. Investigators believe that by building a culvert that intersects pipelines carrying flammable gases, the pipes were exposed to air that caused corrosion and eventually led to the leak of propylene that ignited on July 31. While the city government had said it had no documents showing the existence of the waterway, Wu said Thursday that he had found documents which show it was built about 20 meters away from where it was placed on the original design map. The end result was a 3-m wide, 2.4-m high culvert which runs 186 m long. Wu said construction began in November 1991 and wrapped up in October 1992. He emphasized that that he has turned over the relevant data to prosecutors. (By Hsieh Chia-chen and Lilian Wu)